It has been found in recent years that it is architecturally aesthetic to apply various surface texturing treatments to the exposed surface of concrete structures. These surfaces can have the appearance of brick, stone, wood and various other simulated materials which provide a very pleasing appearance to the overall structure upon completion.
In order to form this surface, negative impression textured liners are provided to be applied to the interior surfaces of the concrete form. These liners are usually made from flexible plastic or rubber-like materials which are quite flimsy and have no supporting structure. As a result these liners are usually cut in relatively small sizes such as 4'.times.8' or 4'.times.10' sheets which are relatively easy to handle and generally fit the standard size panels which are used to make up the concrete forms that are utilized in commercial and residential building construction.
Because of the flexible nature of the liner it has been found to be difficult to work with in an efficient manner. In fact, because of its flexible nature it is necessary to fasten the liner rigidly to the inside surface of the usual concrete forms in order to hold it in place while the concrete is poured into the forms and allowed to set. This attachment to the forms has normally taken place by fasteners or by adhering the liner to the inner surface of the form by means of a suitable adhesive. Most of the adhesives are permanent and thus preclude or greatly limit the reuse capability of the liner. In some cases the liner has been cut to the exact size of the form before or after it is attached. In addition, if the form and liner are carefully handled the form can be reassembled and reused for subsequent construction. The biggest problem that occurs in this reuse is the lack of a reliable edge sea between the form sections which allows the grout to seep between the edges of the form causing a "flashing" or seam to exist along the surface of the finished concrete. Because of this, it takes additional time to grind or remove this flashing from the set concrete in order to finish the surface of the structure.
It has also been found that when the liner is applied to the concrete forms especially in the field problems exist with adhering the liner to the form in order to prevent surface bubbles and loose areas. If this condition occurs the liner in many cases will be torn from the forms when an attempt is made to release the form and the liner from the concrete surface. Thus, additional time and effort is required to remove the form and liner without damaging the finished surface of the concrete.
It is well known in the trade that when concrete forms are made of plywood the panels must be coated with oil as a parting agent in an attempt to prevent the penetration of the cement water into the wood. Experience has shown that plywood panels rarely last more than three or four pours because of this and more particularly because the corners and edges are easily damaged in the form construction, shipping and storing. In addition, cement water draining from the concrete enters the cracks of the plywood joints and any damaged surface areas of the panels causing rapid deterioration and warping of the panel. Thus, even though plywood is the most common and lowest original cost forming media, it is quite restrictive and limited in its reuse which adds greatly to the overall cost of the concrete construction.
In the present invention the applicant has found a very novel and unique way of making and using a plywood form liner which is rigid and easy to handle as well as eliminating edge leakage even though the form liner may be reused a considerably number of times.